This invention relates to packet voice transmission.
Communications networks currently transfer vast quantities of information in both local and wide area networks. The information typically consists of signals representing digitized voice and video as well as data that are transferred between endpoints in networks. A communication path may be established in such networks by circuit switching or by packet switching. In circuit switching, an exclusive channel is established between a sender and a receiver throughout the entire transmission until the connection is released. In packet switching, virtual circuits or channels are established between a sender and a receiver and a channel is only occupied for the duration of the packet's transmission. Such packet switching enables networks to handle the heterogeneous mix of network traffic with varying service requirements and, ideally, packet switching is scalable and can reliably establish and maintain virtual channels without any prespecified rates (so-called bandwidth on demand).
There is currently a significant interest in integrating packet voice in the next generation of broadband data systems in order to provide packet telephony capabilities. The difficulty with establishing packetized voice in the conventional virtual circuit approach described above, is that either delay or clipping is suffered. That is, when a speaker goes silent and the path is released to other users, when the speaker resumes the conversation there may be a period of time during which there is no bandwidth available for the conversation. During such time, the speech signal might be stored and forwarded when bandwidth does become available, or a portion of the speech might be clipped. Neither is a desirable consequence.